Camco Plastic Blow Out Plug is used to apply air pressure to your water lines to ensure that all of the water is removed before winterizing. With less water remaining in the lines, your anti-freeze will work at the dilution you want. Just screw the plug into the city water inlet, open all drains and faucets, attach and activate the oil-less air compressor until all lines are clear. Durable plastic construction will not rust. Use prior to winterizing your RV to clear water lines and avoid diluting antifreeze Screw the plug into your RV's city water inlet to blow air through the lines Incorporates a Schrader valve connection that allows use with most compressors Durable plastic construction - will not rust Easy to use